Untersuchung der Metall/Elektrolyt-Grenzflaeche mit Oberflaechenroentgenbeugung

In this work the structure of the metal/electrolyte interface was characterized by in-situ X-ray surface diffraction (XRSD). For this purpose an electrochemical cell was developed which allowed the simultaneous application of the XRSD technique and the method of cyclic voltammetry. The cell is constructed in such a way that it operates in a thin layer mode during the X-ray scattering experiments and is filled with electrolyte for the recording of cyclic voltammograms. With this cell the following metal/electrolyte interfaces were investigated: Au(100)/aqueous HClO_4, Au(100)/aqueous H_2SO_4, Pt(100)/aqueous HClO_4, Pt(111)/aqueous H_2SO_4. In all cases the single crystal surfaces are unreconstructed under the given experimental conditions and exhibit a certain island coverage and vacancy density depending on the surface orientation. No anion adsorption effect could be detected by XRSD except in the case of the Au(100)/aqueous H_2SO_4 interface. The analysis revealed an ordered commensurable adsorption layer of sulfate or hydrogensulfate ions with an coverage of about (35#+-#10)%. However, no definite adsorption structure could be determined as shown in the discussion. On the basis of the results of the clean single crystal surfaces in contact with an electrolyte the structure and electrochemical behaviour of copper underpotential deposition (UPD) on Au(100) and ruthenium deposition on Pt(100) and Pt(111) were characterized. (orig.)Available from FIZ Karlsruhe / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman